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54 PROCESS, MATERIALS, AND MEASUREMENTS
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FORMING (METAL)
Forming is the process of transforming a specified material into a desired shape.
This section describes processes for forming cold and molten metal.
Casting
is a process by which molten metal is poured into a mold and allowed
to harden.
Sand casting
involves creating a master pattern that is pressed into a bed of sand
mixed with a heat resistant binder, resulting in a single-use (expendable) sand mold.
The mold includes a sprue, which channels molten metal into the part cavity, runners
for distributing the metal throughout the mold, and vents that allow gases to escape.
After the metal cools and hardens, the mold is broken away to remove the part. Sand
casting requires secondary processes to trim away the sprue, runners, and other
extraneous parts.
C
Investment casting
involves creating a master pattern made of a material that melts
or evaporates when subjected to heat. The pattern is packed in sand or dipped in
ceramic slurry. In the situations where ceramic is used, it is allowed to harden and
the mold is inverted, then heated, allowing the pattern to melt away. Molten metal is
poured into the mold. After the metal cools and hardens, the mold is broken away.
Investment cast parts require secondary processes to trim away extraneous parts.
SAND CASTING
Gate
Peripheral
Feeder Rings
Radial Feeders
to Mold Cavity
Vents to Exhaust
Air and Gases
Alignment
Pins
Mold Parting
Plans
Mold Cavities Formed
by Packing Sand
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Manufacturing Process
Die casting
involves forcing molten metals into reusable molds using pressure.
Metals with lower melting points (aluminum, copper, zinc, etc.) are used with this
process. When the parts cool and harden, they require secondar y operations to
remove flash.
Contour roll forming
is a process by which metal strips or sheets are converted into
continuous section profiles through a sequence of mating rollers. Each set of rollers
in the sequence progressively bends the strip until it reaches the desired section.
This process adds strength and rigidity to flat materials.
CONTOUR ROLL FORMING
Step 1
Step 2
Step 3
Step 4
Step 5
INVESTMENT CASTING
Pattern Cluster Flask Molding Shell Mold
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56 PROCESS, MATERIALS, AND MEASUREMENTS
Deep draw (stamping)
is a process that produces hollow shapes from flat sheets of
metal. The process involves a punch pushing a blank sheet of metal into a cavity.
Secondary trim operations are often necessary.
Extrusion
is a process by which molten metal (usually aluminum) is forced through a
die to form a long continuous section profile. Tooling costs are lower when compared
to other processes, and little scrap is produced. Designing a part with a continuous
section is important in preventing curvature in the length. Extrusions can be cut to a
desired length, and secondary operations are used to polish or add features through
material removal.
Punch
Punch
Ejector
Blank
Cavity
DEEP DRAW (STAMPING)
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Forging
is a process of compressively deforming metal (heated or cold) between two
dies using impact or pressure. Forging can be used to form parts of almost any size
and shape and is commonly used for tools and fasteners.
Hydroforming
is a process for creating complex formed metal parts, without the need
for costly matched die pairs. The process utilizes pressurized liquid to force sheet
metal into a single die cavity.
Spinning
is a process for producing hollow rounded shapes by forcing a spinning
metal blank against a pattern. This process yields accurate and cost-effective parts.
SPINNING
Headstock
rotates
workplace
Spinning tool
Tailstock
Tool rest has
protruding pins
serving as pivots
for spinning tools
Blank
Chuck
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